<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        *{
            margin: 0px;
            padding: 0px;
        }
        .btn{
            
            width: 100px;
            height: 30px;
            background-color: brown;
            border: 0px;
            color: white;
            flex-grow: 1;
            border: 1px solid greenyellow;
            text-align: center;

        }
        span{
            transition: 1s;
            line-height: 30px;
        }
        .btn:hover{
            background-color: rgb(199, 101, 101);
        }
        .btn:hover span{ 
            padding-right: 10px;
            display: inline;
        }
        .parte{
            width: 100%;
            display: flex;
        }
        .btn:hover .list{ 
            display: block;
            position: relative;
            top: 0px;
        }
        .list{
            position: relative;
            top: -300px;
            width: 100%;
            height: 300px;
            background-color: aquamarine;
            transition: 0.5s;
            z-index: -1;
            overflow-x: -1;
        }
        .itme{
            width: 100%;
            height: 48.5px;
            border: 1px solid grey;
        }
    </style>
</head>
<body>
    
    <div class="parte">
        <div class="btn">
            <span>按钮1</span><span>&lt;&lt;</span>
            <div class="list">
            <div class="itme">列表</div>
            <div class="itme">列表</div>
            <div class="itme">列表</div>
            <div class="itme">列表</div>
            <div class="itme">列表</div>
            <div class="itme">列表</div>
            </div>

        </div>
        <div class="btn">
            <span>按钮2</span>
            <div class="list">11</div>
        </div>
        <div class="btn">
            <span>按钮3</span>
            <div class="list">11</div>
        </div>
        <div class="btn">
            <span>按钮4</span>
            <div class="list">11</div>
        </div>
        <div class="btn">
            <span>按钮5</span>
            <div class="list">11</div>
        </div>
        
    </div>

</body>
</html>